The preparation of powdered detergent formulations by mechanical mixing methods based on the sodium salt of anionic surfactants and certain nonionic surfactants in the past has generally led to poor powder processing characteristics of the detergent formulation.
The poor processing characteristics of these detergent formulations have been due to a variety of reasons, among which, for example, is that an excessive amount of water is usually associated with the anionic component of the detergent formulation and the hygroscopic nature of the surfactants themselves. Also incompatability of the nonionic surfactant with the electrolyte or builder component of the formulation has led to "bleeding" of the nonionic surfactant into a separate phase on the surface of the solid particles.
The importance of preparing these detergent formulations by mechanical means is becoming increasingly important because of the low energy requirements and cost savings that are realized as compared to other means of preparing anionic, nonionic, and mixed powdered detergent formulations known in the art. Previous attempts at overcoming the aforementioned problems have included the addition of processing aids, for example, clays, which act as absorbents for the organic components in the formulations (Netherlands Patent No. 7,413,521). Applicant has surprisingly discovered, however, that a much better approach in overcoming the processing problems of these nonionic based, powdered detergent formulations is by the use of relatively insoluble calcium salts of non-soap organic, anionic detergent surfactants in the formulations. Unexpectedly, these calcium salts do not significantly lower the detergent properties of the powder formulations relative to the corresponding formulation utilizing the sodium salt of the anionic surfactant.
The use of alkali metal salts of anionic surfactants in detergent compositions to improve the detergency benefits thereof has been cited in various publications known in the prior art. Examples of the prior art are as follows:
U.s. pat. No. 2,908,651 issued on Oct. 13, 1959; PA1 U.s. pat. No. 2,691,636 issued on Oct. 12, 1954; PA1 U.s. pat. No. 2,766,212 issued on Oct. 9, 1956; PA1 U.s. pat. No. 3,718,609 issued on Feb. 23, 1973; PA1 U.s. pat. No. 3,686,098 issued on Aug. 22, 1972; PA1 U.s. pat. No. 2,437,253 issued on Mar. 9, 1948; and PA1 Australian Patent No. 18/76 published July 21, 1976.
Applicant has discovered, however, that the selection of the calcium salt of certain organic, synthetic, non-soap anionic surfactants in combination with a selected class of nonionic surfactants and the alkali metal salt of a builder compound that will precipitate hardness ions in water, has a significant effect in the preparation of powdered detergent formulations by mechanical means, while at the same time increasing the cold water detergency of such formulations as well as maintaining the overall detergency properties thereof. The prior art fails to recognize the problems encountered with mechanically mixed, nonionic based detergent products, and how they may be overcome. It is an object of the present invention, therefore, to provide mechanically mixed, powdered detergent compositions in an efficient manner and which will overcome the problems known heretofore in their manufacture, while at the same time maintaining good detergency properties, especially in regard to cold water detergency performance.
All percentages are expressed by weight unless otherwise specified.